Progesterone plays a fundamental role in the establishment and maintenance of earlypregnancy. After ovulation or egg retrieval, the corpus luteum — a temporary gland formed in the ovary — produces progesterone, which transforms the uterine lining (endometrium) into a receptive, nutrient-rich environment where the embryo can implant and thrive. When pregnancy occurs, the early embryo produces human chorionic gonadotropin (hCG), which signals the corpus luteum to continue producing progesterone. This ensures stability of the uterine lining until the placenta takes over hormone production around the 10th to 12th week of gestation.
In assisted reproductive treatments such as in vitro fertilization (IVF), the natural production of progesterone can be disrupted due to ovarian stimulation or egg retrieval. Therefore, exogenous progesterone supplementation — through vaginal, oral, or injectable forms — is prescribed to mimic the body’s natural cycle and prevent luteal phase deficiency. Continuing progesterone after a positive pregnancy test is critical because stopping too soon may lead to a drop in hormone levels, resulting in uterine contractions or shedding of the endometrial lining, which could threaten the developing pregnancy.
Maintaining progesterone support until placental autonomy ensures the embryo remains securely implanted and nourished. Clinically, it has been demonstrated that sustained progesterone supplementation significantly reduces the risk of early miscarriage, particularly in IVF cycles and in patients with a history of luteal insufficiency.
In summary, progesterone acts as the “guardian hormone” of early pregnancy — maintaining endometrial integrity, reducing uterine activity, and promoting embryonic stability until the placenta assumes full hormonal responsibility. Continuing it beyond a positive pregnancy test is essential for securing a healthy start to gestation.
